Random sampling involves selecting a sample where each element of the sample have an equal probability of selection.
From the question, we understand that the director wants to make use of a stratified random sampling technique.
The stratified random sampling technique involves selecting the sample (i.e. 100 students), by dividing the whole undergraduate students into groups (i.e. strata), and then select a proportion from each group.
A possible way to achieve this, is as follows:
With the above highlights, the director would be able to make the selection.
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